Nucleotide excision repair (NER) is the major DNA repair mechanism that removes bulky DNA damage products caused by UVB radiation as well as other environmental carcinogens. As a subtype of canonical NER, global genome NER (GG-NER) repairs DNA damage across the whole genome, and is essential for preventing skin cancer, the most common cancer in the US, as well as cancers in the brain and lungs 1-7. However, the molecular mechanism of regulating GG-NER capacity remains poorly understood. Recently, we discovered a novel role for METTL14 (methyltransferase-like 14), as a key component of the N6- methyladenosine (m6A) RNA methyltransferase and writer, in promoting GG-NER and suppressing tumor growth. m6A RNA methylation is the most abundant internal chemical modification in eukaryotic messenger RNA (mRNA) as well as long non-coding RNA (lncRNA). m6A modification regulates the fate of RNA and its functions, such as mRNA stability, nuclear processing, transport, localization, translation, primary microRNA processing, and RNA-protein interactions. The goal of this proposal is to determine the mechanism by which METTL14, as a key m6A writer, regulates GG-NER and UVB-induced skin cancer. Our preliminary data suggest that METTL14, as a key m6A writer protein, plays a critical role in regulating GG-NER and skin tumorigenesis. Thus we hypothesize that METTL14, as a key m6A writer, plays a critical role in GG-NER and UVB-induced skin cancer through posttranscriptionally regulating the expression of its essential target genes. To test this hypothesis, we will employ several new methods including transcriptome-wide m6A mapping, eCLIP-seq, and RIP-seq. In addition, we will use a new mouse model with skin-specific METTL14 deletion. Our hypothesis will be tested in three Specific Aims. Aim 1 will determine the mechanism by which METTL14 regulates GG-NER. Aim 2 will determine the mechanism by which UVB radiation down-regulates METTL14. Aim 3 will determine the consequences of METTL14 inhibition in UVB-induced skin tumorigenesis in mice. Successful completion of our proposed project may vastly expand our knowledge of GG-NER regulation and tumor suppression by METTL14 and m6A RNA methylation, providing new opportunities for developing better strategies to prevent and treat skin cancer by targeting the METTL14 pathway. Caners arise in the skin more than in any other organ site, most likely due to environmental damage. In addition, our work here in GG-NER and METLL14 is not only significant in skin cancer, but is also applicable to other tumor types as well.